Aqueous fluoromodified polyurethane system for anti-graffiti and anti-soiling coatings

ABSTRACT

An aqueous fluoromodified polyurethane system for one- or two-component anti-graffiti and anti-soiling coatings is described which is obtainable by 
     (a) preparing a binder component based on an aqueous solution or dispersion of optionally hydroxy- and/or amino-functional oligourethanes and/or polyurethanes having fluorinated side chains, and, optionally,  
     (b) subsequently reacting the binder component with a crosslinker component.  
     Surprisingly it has been found that the hydrophobicization of the binder component that is brought about by the fluorinated side groups present in the oligo- or polyurethane polymer does not lead to an increase in the anionic hydrophilicization with salt groups and that the cured films have very low surface energies even with very low fluorine contents.  
     The aqueous highly crosslinked anti-graffiti and anti-soiling polyurethane coating systems proposed in accordance with the invention are suitable, individually or in combination, for constructing systems for 
     (α) dirt-repellent anti-graffiti coatings on plastic, wood or metal,  
     (β) dirt-repellent coatings of rotors for wind power plants, and also  
     (γ) dirt-repellent interior floor coverings and exterior ground coverings.

[0001] The present invention relates to an aqueous fluoro-modified one-or two-component polyurethane system for antigraffiti and antisoilingcoatings, based on an aqueous solution or dispersion of optionallyhydroxy- and/or amino-functional oligourethanes and/or polyurethaneshaving fluorinated side chains as binder component and optionallywater-emulsifiable polyisocyanates as crosslinker component, and to itsuse.

[0002] The majority of polymer high-performance coating materials,although having very good mechanical properties, possess high surfaceenergies. Through targeted chemical modification of these systems withfluorinated building blocks it is possible to combine the specificsurface properties of the fluorinated materials with the individualproperties of the base polymers or copolymers. It proves advantageoushere that often only small amounts of the expensive fluoro compounds areneeded in order to achieve the desired surface properties.

[0003] The increase in demand for soil-repellent, weathering-resistantcoatings has led in recent times to the development of newfluoropolymers for coating systems that no longer have the disadvantagesof conventional fluoropolymers. This new generation offluorocarbon-based polymers for coating systems are soluble in commonorganic solvents, can be cured even at standard temperature, and exhibitimproved compatibility with commercial curing agents.

[0004] Within coating technology increasing importance has been attachedin recent years to environmental aspects, including that relating tocompliance with existing emissions guidelines. A particularly urgentconcern is to reduce the amounts of volatile organic solvents (VOCs,volatile organic compounds) used in coating systems.

[0005] The binder class of the aqueous or water-based polyurethanes, asan alternative to conventional solvent-based polyurethane systems, hasbeen known for more than 40 years. The profile of properties of theaqueous polyurethanes has been continuously improved in the decades goneby, as forcefully evidenced by a multiplicity of patents andpublications on this topic area. On the chemistry and technology ofwater-based polyurethanes reference may be made to D. Dieterich, K.Uhlig in Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition2001 Electronic Release. Wiley-VCH; D. Dieterich in Houben-Weyl,Methoden der Organischen Chemie. Vol. E20, H. Bartl, J. Falbe (eds.),Georg Thieme Verlag, Stuttgart 1987, p. 1641 ff.; D. Dieterich, Prog.Org. Coat. 9 (1981) 281-330; J. W. Rosthauser, K. Nachtkamp, Journal ofCoated Fabrics 16 (1986) 39-79; R. Arnoldus, Surf. Coat. 3 (WaterborneCoat.) (1990), 17998.

[0006] Aqueous two-component polyurethane systems with low cosolventcontent or featuring extreme VOC reduction, which in view of their highlevel of properties are of great importance in coating systems, havesince come, in conjunction with water-emulsifiable polyisocyanate curingsystems for chemical postcrosslinking, to represent an alternative tothe corresponding solventborne systems.

[0007] Water-based copolymer dispersions or emulsions based on monomerscontaining perfluoroalkyl groups, have been known for a fairly longtime. They are used for the hydrophobicization and oleophobicization,particularly of textiles or carpets, both alone and in conjunction withother textile assistants, provided the perfluoroalkyl groups are linearand contain at least 6 carbon atoms.

[0008] For the preparation of these copolymer dispersions and emulsionsvia emulsion polymerization a variety of emulsifier systems are usedand, depending on the nature of the emulsifier system used, anionicallyor cationically stabilized copolymer dispersions or emulsions areobtained which have different performance properties.

[0009] Aqueous dispersions of graft copolymers containing perfluoroalkylgroups and their use as hydrophobicizing and oleophobicizing agents havealready been known from the patent literature for some time.

[0010] EP 0 452 774 A1 and DE 34 07 362 A1 describe a process forpreparing aqueous dispersions of copolymers and/or graft copolymers fromethylenically unsaturated perfluoroalkyl monomers and non-fluoromodifiedethylenically unsaturated monomers, using aqueous, emulsifier-freepolyurethane dispersions as the graft base.

[0011] DE 36 07 773 C2 describes polyurethanes which containperfluoroalkyl ligands and which are used in the form of an aqueousdispersion, but using external emulsifiers, or in the form of a solutionin an organic solvent (mixture), exclusively for the treatment oftextile materials and of leather.

[0012] Polyurethanes containing perfluoroalkyl groups for the oleophobicand hydrophobic treatment of textiles are also described in patents DE14 68 295 A1, DE 17 94 356 A1, DE 33 19 368 A1, EP 0 103 752 A1, U.S.Pat. No. 3,398,182 B1, U.S. Pat. No. 3,484,281 B1 and U.S. Pat. No.3,896,251 B1.

[0013] These compounds, however, require large quantities forapplication and exhibit inadequate adhesion to the substrate.

[0014] WO 99/26992 A1 describes aqueous fluoro- and/or silicone-modifiedpolyurethane systems having low surface energies, which cure towater-stable and solvent-stable, hard polyurethane films havinganti-fouling properties. The claims therein embrace the following twoperfluoroalkyl components:

R_(f)—SO₂N—(R_(h)—OH)₂

[0015] (where R_(f)=perfluoroalkyl group having 1-20 carbon atoms andR_(h)=alkyl group having 1-20 carbon atoms) and

R_(f)R′_(f)CF—CO₂CH₂CR(CH₂OH)₂

[0016] (where R_(f)=C₄-C₆ fluoroalkyl, R′_(f)=C₁-C₃ fluoroalkyl, andR=C₁-C₂ alkyl)

[0017] Water-dispersible sulfo-polyurethane or sulfo-polyureacompositions with low surface energy, especially for ink-absorbingcoatings, are described in EP 0 717 057 B1, the hydrophobic segmentsbeing composed of polysiloxane segments or of a saturatedfluoroaliphatic group having 6-12 carbon atoms, of which at least 4 arefully fluorinated. Aqueous dispersions of water-dispersiblepolyurethanes having perfluoroalkyl side chains, without the use ofexternal emulsifiers, are described in EP 0 339 862 A1. Theisocyanate-reactive component used there is a fluorinated polyolobtained by free radical addition of a polytetramethylene glycol with afluorinated olefin (see EP 0 260 846 A1). The polyurethane dispersionsobtained, however, all possess solids contents of less than 30% byweight and, moreover, require considerable amounts of hydrophiliccomponent. The surface energies of the dried films are still >30 dynecm⁻¹.

[0018] The present invention was based, therefore, on the object ofdeveloping a system for antigraffiti and antisoiling coatings havingimproved material properties and application properties taking intoaccount environmental, economic, and physiological factors.

[0019] This object has been achieved in accordance with the inventionthrough the provision of an aqueous, soil-repellent, one- ortwo-component polyurethane system having fluorinated side chains. Thesystem comprises a binder component and optionally a crosslinkercomponent. The system of the invention is obtainable by

[0020] (a) preparing a binder component based on an aqueous solution ordispersion of low molecular mass, hydroxyl- and/or amino-functionaloligo- and/or polyurethanes, for which

[0021] (a₁) from 2.5 to 12 parts by weight of a fluoromodified polyolcomponent (A)(i) having two or more isocyanate-reactive hydroxyl groupsand an average molecular mass of from 500 to 2 000 daltons, from 10 to50 parts by weight of a high molecular mass polyol component (A)(ii)having two or more polyisocyanate-reactive hydroxyl groups and anaverage molecular mass of from 500 to 6 000 daltons, and from 0 to 10parts by weight of a low molecular mass polyol component (A) (iii)having two or more polyisocyanate-reactive hydroxyl groups and anaverage molecular mass of from 50 to 499 daltons are reacted with from 2to 30 parts by weight of a polyisocyanate component (B), composed of atleast one polyisocyanate, polyisocyanate derivative or polyisocyanatehomolog having two or more aliphatic or aromatic isocyanate groups, withthe addition of from 0 to 25 parts by weight of a solvent component (C)composed of an inert organic solvent, optionally in the presence of acatalyst,

[0022] (a₂) the polyurethane preadduct from stage (a₁) is reacted,optionally in the presence of a catalyst, with from 1 to 10 parts byweight of a low molecular mass, anionically modifiable polyol componentor polyamine component (A) (iv) having two or morepolyisocyanate-reactive hydroxyl and/or amino groups and one or moreinert carboxylic and/or sulfonic acid groups, some or all of which canbe converted by means of bases into carboxylate and/or sulfonate groups,respectively, or are already in the form of carboxylate and/or sulfonategroups, having an average molecular mass of from 100 to 1 000 daltonsand/or with from 0 to 20 parts by weight of a polymeric diol component(A) (v) having two or more polyisocyanate-reactive hydroxyl groups andfurther, polyisocyanate-inert, hydrophilic groups, having a molecularmass of from 500 to 5 000 daltons,

[0023] (a₃) some or all of the free isocyanate groups of thepolyurethane prepolymer from stage (a₂) are reacted with from 0 to 15parts by weight of a polyfunctional chain terminator component (D)having three or more isocyanato-reactive hydroxyl and/or primary and/orsecondary amino groups and an average molecular mass of from 50 to 500daltons, of which one reacts with the polyurethane preadduct,

[0024] (a₄) the polyfunctional polyurethane oligomer or polymer fromstage (a₃) is admixed, for neutralization of some or all of the acidgroups, with from 0.1 to 10 parts by weight of a neutralizing component(E), and then

[0025] (a₅) the neutralized polyurethane oligomer or polymer from stage(a₄) is dispersed in from 40 to 120 parts by weight of water, which mayalso contain from 0 to 50 parts by weight of a formulating component(F), and

[0026] (a₆) the only partly chain-terminated polyurethane oligomer orpolymer from stage (a₅) is further reacted with from 0 to 10 parts byweight of a chain extender component (G) having two or moreisocyanato-reactive primary and/or secondary amino groups and amolecular mass of from 50 to 500 daltons,

[0027] and, optionally,

[0028] (b) subsequently reacting the binder component from stages (a₄),(a₅) or (a₆) with from 20 to 100 parts by weight of a crosslinkercomponent (H), said crosslinker component (H) comprisingwater-dispersible polyisocyanates having aliphatically and/orcycloaliphatically and/or aromatically attached isocyanate groups andpossibly containing from 0 to 20 parts by weight of an organic solvent.

[0029] Surprisingly it has been found that the hydrophobicization of thebinder component that is brought about by means of the fluorinated sidegroups present in the oligourethane or polyurethane polymer does notlead to an increase in anionic hydrophilicization with salt groups(30-45 meq/100 g resin solids) and that the fully cured films have verylow surface energies even with very low fluorine contents (from 0.5 to5% by weight and preferably from 0.5 to 2.0% by weight, based on theresin solids).

[0030] In the two-component application it is also possible toincorporate the crosslinker component, particularly polyisocyanateswithout permanent hydrophilic modification, into the fully modifiedbinder component very easily by means of simple emulsifying techniques:for example, by using a mechanical stirrer or by means of simple mixingof the two components by hand. This ensures fine, homogeneousdistribution of the polyisocyanate droplets in the binder component.

[0031] The aqueous fluoromodified polyurethane system of the inventionfor anti-graffiti and antisoiling coatings is defined by a multistagepreparation process. In reaction stage (a), first of all, a low-solventor solvent-free binder component is prepared on the basis of an aqueoussolution or dispersion of optionally hydroxy- and/or amino-functionaloligomer- or polyurethanes having fluorinated side chains and thisbinder component is then optionally reacted further in reaction stage(b) with a crosslinker component based on water-dispersiblepolyisocyanates to give an aqueous, highly crosslinked two-componentpolyurethane coating system.

[0032] The binder component is prepared by means of a modifiedprepolymer mixing process, called the high solids process (HSPtechnology). High shear forces are unnecessary here, and so, forexample, high-speed stirrers, dissolvers or rotor/stator mixers can beused.

[0033] To implement this process, employing the techniques customary inpolyurethane chemistry, in reaction stage (a₁) from 2.5 to 12 parts byweight of a fluoromodified polyol component (A) (i), from 10 to 50 partsby weight of a high molecular mass polyol component (A)(ii), andoptionally from 0 to 10 parts by weight of a low molecular mass polyolcomponent (A) (iii) are reacted with from 2 to 30 parts by weight of apolyisocyanate component (B), with the addition of from 0 to 25 parts byweight of a solvent component (C), optionally in the presence of acatalyst, the reaction being carried out partially or completely, withsome or all of the hydroxyl groups of components (A)(i), (A)(ii), and(A) (iii) being reacted with the isocyanate groups of component (B).

[0034] The preparation of the polyurethane preadduct in accordance withreaction stage (a₁) preferably takes place in a manner such that firstof all component (B) is added within a period of a few minutes tocomponent (A) (i), optionally in solution in component (C), andsubsequently a mixture of components (A)(ii), (A)(iii), and, optionally(C), is added or metered in over a period ranging from a few minutes toa few hours or, alternatively, the mixture of components (A)(i),(A)(ii), (A) (iii), and, optionally, (C) is added or metered in tocomponent (B) over a period ranging from several minutes to severalhours. In order to reduce the viscosity it is possible to use smallamounts of a solvent component (C) in reaction stage (a₁).

[0035] The fluoromodified polyol component (A)(i) contains two or moreisocyanate-reactive hydroxyl groups and has an average molecular mass of500-2 000 daltons (number average). It is preferably composed of thereaction product or macromonomer of monofunctional fluoroalcohols,aliphatic and/or aromatic diisocyanates, and a dialkanolamine,especially diethanolamine. Fluoroalcohols which can be used includeperfluoroalkyl alcohols having terminal methylene groups (hydrocarbonspacers) of the general formula

F(CF₂)_(x)—(CH₂)_(y)—OH

[0036] with x=4-20 and y=1-6

[0037] and also commercial mixtures of these (e.g. Zonyl® BA, Du Pont deNemours) or hexafluoropropene oxide (HFPO) oligomer alcohols of thegeneral formula

CF₃CF₂CF₂O—(CF(CF₃)CF₂O)_(z)—CF(CF₃)CH₂—OH,

[0038] with z=1-10

[0039] (e.g. Krytox® Du Pont de Nemours) or else mixtures of both.

[0040] The fluoroalcohol is first added dropwise to the correspondingdiisocyanate over a period of 30-60 minutes at a temperature between 0and 30° C., with the addition of a catalyst and also of a suitablesolvent, and is reacted in such a way that only one isocyanate group isreacted. In a further step the resultant preadduct is introduceddropwise into diethanolamine over the course of several minutes, withcooling.

[0041] Suitable solvents are, for example, N-methylpyrrolidone (NMP) ortetrahydrofuran.

[0042] Customary catalysts for polyaddition reactions withpolyisocyanates are, for example, dibutyltin oxide, dibutyltin dilaurate(DBTL), triethylamine, tin(II) octoate, 1,4-diazabicyclo[2.2.2]octane(DABCO), 1,4-diazabicyclo[3.2.0]-5-nonene (DBN), and1,5-diazabicyclo[5.4.0]-7-undecene (DBU).

[0043] The polyol component (A) (ii) is composed of a high molecularmass polyol having two or more polyisocyanate-reactive hydroxyl groupsand an average molecular mass (number average) of from 500 to 6 000daltons. Suitable polymeric polyols which can be used includepolyalkylene glycols, aliphatic or aromatic polyesters,polycaprolactones, polycarbonates, α,ω-polymethacrylatediols,α,ω-dihydroxyalkylpolydimethylsiloxanes, hydroxy-functionalmacromonomers, hydroxy-functional telecheles, hydroxy-functional epoxyresins or suitable mixtures thereof.

[0044] Suitable polyalkylene glycols are, for example, polypropyleneglycols, polytetramethylene glycols or polytetrahydrofurans,hydrophobically modified polyether polymers composed ofsaponification-stable block copolymers with an ABA, BAB or (AB)_(n)structure, in which A represents a polymer segment havinghydrophobicizing properties and B a polymer segment based onpolypropylene oxide, hydrophobically modified polyetherpolyols composedof saponification-stable block copolymers with an A₁A₂A₃ or (A₁A₂)_(n)structure, in which A in each case represents polymer segments havinghydrophobicizing properties, and hydrophobically modified randompolyetherpolyols composed of saponification-stable random copolymers ofat least one hydrophobic alkylene oxide and propylene oxide.

[0045] It is preferred to use linear or difunctional hydrophobicallymodified polyether polymers composed of saponification-stable blockcopolymers with an ABA, BAB or (AB)_(n) structure, in which A representsa polymer segment having hydrophobicizing properties and B a polymersegment based on polypropylene oxide, having an average molecular mass(number average) of from 1 000 to 3 000 daltons.

[0046] Suitable aliphatic or aromatic polyesters are, for example,condensates based on 1,2-ethanediol or ethylene glycol and/or1,4-butanediol or 1,4-butylene glycol and/or 1,6-hexanediol or1,6-hexamethylene glycol and/or 2,2-dimethyl-1,3-propanediol orneopentyl glycol and/or 2-ethyl-2-hydroxymethyl-1,3-propanediol ortrimethylolpropane and also 1,6-hexanedioic acid or adipic acid and/or1,2-benzenedicarboxylic acid or phthalic acid and/or1,3-benzenedicarboxylic acid or isophthalic acid and/or1,4-benzenedicarboxylic acid or terephthalic acid and/or sodium5-sulfoisophthalate and/or esters thereof, and also reaction products ofepoxides and fatty acids. It is preferred to use linear or difunctionalaliphatic or aromatic polyester polols having an average molecular mass(number average) of from 1 000 to 3 000 daltons.

[0047] Polycaprolactones based on E-caprolactone (CAPA grades, SolvayInterox Ltd.), polycarbonates based on dialkyl carbonates and glycols(Desmophen 2020, Bayer AG), and combinations (Desmophen C 200, Bayer AG)likewise belong to the polyesters group. It is preferred to use linearor difunctional types having an average molecular mass (number average)of from 1 000 to 3 000 daltons.

[0048] As α,ω-polymethacrylatediols (TEGO® Diol BD 1000, TEGO® Diol MD1000 N, TEGO® Diol MD 1000 X, Tego Chemie Service GmbH) having amolecular mass of from 1 000 to 3 000 daltons andα,ω-dihydroxyalkylpolydimethyl-siloxanes it is preferred to use linearor difunctional types having an average molecular mass (number average)of from 500 to 3 000 daltons.

[0049] Component (A) (iii) is composed of a low molecular mass polyolhaving two or more polyisocyanate-reactive hydroxyl groups and anaverage molecular mass (number average) of from 50 to 499 daltons. Assuitable low molecular mass polyols it is possible to use, for example,1,2-ethanediol or ethylene glycol, 1,2-propanediol or 1,2-propyleneglycol, 1,3-propane-diol or 1,3-propylene glycol, 1,4-butanediol or1,4-butylene glycol, 1,6-hexanediol or 1,6-hexa-methylene glycol,2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol or neopentylglycol, 1,4-bis(hydroxymethyl)cyclohexane or cyclohexane-dimethanol,1,2,3-propanetriol or glycerol,2-hydroxy-methyl-2-methyl-1,3-propanediol or trimethylolethane,2-ethyl-2-hydroxymethyl-1,3-propanediol or trimethylol-propane,2,2-bis(hydroxymethyl)-1,3-propanediol or pentaerythritol, or mixturesthereof. Preference is given to using 1,4-butanediol.

[0050] The polyisocyanate component (B) is composed of at least onepolyisocyanate, polyisocyanate derivative or polyisocyanate homologhaving two or more aliphatic or aromatic isocyanate groups. Particularlysuitable are the polyisocyanates well known in polyurethane chemistry,or combinations thereof. As suitable aliphatic polyisocyanates it ispossible to use, for example, 1,6-diisocyanatohexane (HDI),1-isocyanato-5-isocyanatomethyl-3,3,5-trimethylcyclohexane oriso-phorone diisocyanate (IPDI), bis(4-isocyanatocyclo-hexyl)methane(H₁₂MDI), 1,3-bis(1-isocyanato-1-methyl-ethyl)benzene (m-TMXDI) and/ortechnical-grade isomer mixtures of the individual aromaticpolyisocyanates. As suitable aromatic polyisocyanates it is possible touse for example, 2,4-diisocyanatotoluene or toluene diisocyanate (TDI),bis(4-isocyanatophenyl)methane (MDI) and, optionally, its higherhomologs (polymeric MDI), and/or technical-grade isomer mixtures of theindividual aromatic polyisocyanates. Also suitable, in principle,furthermore, are the “paint polyisocyanates”, as they are called, basedon bis(4-isocyanatohexyl)methane (H₁₂MDI), 1,6-diisocyanatohexane (HDI),and 1-isocyanato-5-isocyanatomethyl-3,3,5-trimethylcyclohexane (IPDI).The term “paint polyisocyanates” characterizes derivatives of thesediisocyanates that contain allophanate, biuret, carbodiimide,isocyanurate, uretdione and/or urethane groups and in which the residualmonomeric diisocyanate content has been reduced to a minimum, inaccordance with the state of the art. Besides these, it is also possibleto use modified polyisocyanates obtainable, for example, by hydrophilicmodification of “paint polyisocyanates” based on 1,6-diisocyanatohexane(HDI). The aliphatic polyisocyanates are preferred to the aromaticpolyisocyanates. Furthermore, polyisocyanates having isocyanate groupsdiffering in reactivity are preferred.

[0051] The NCO/OH equivalent ratio of components (A) and (B) is adjustedto a figure of from 1.2 to 2.5, preferably from 1.5 to 2.25.

[0052] Preference is given to using polyisocyanates containingisocyanate groups differing in reactivity, so as to give narrowermolecular mass distributions with lower polydispersity. Accordingly,preference is given to polyurethane prepolymers with a linear structure,which are composed of difunctional polyol components and polyisocyanatecomponents. The viscosity of the polyurethane prepolymers is preferablylow and largely independent of the structure of the polyol andpolyisocyanate components used.

[0053] The solvent components (C) is composed of an inert organicsolvent. As suitable organic solvents it is possible, for example, touse low-boiling solvents, such as acetone and methyl ethyl ketone, orhigh-boiling solvents, such as N-methylpyrrolidone and dipropyleneglycol dimethyl ether (Proglyde DMM®). Following preparation, thelow-boiling organic solvents can be removed again, if desired, byredistillation. In accordance with one particularly preferred embodimentthe polyurethane dispersion contains less than 10% by weight of organicsolvents.

[0054] In the subsequent reaction stage (a₂) the partially or completelyreacted polyurethane preadduct from stage (a₁) is reacted with from 1 to10 parts by weight of a low molecular mass, anionically modifiablepolyol component (A) (iv) and/or with from 0 to 20 parts by weight of apolymeric diol component (A)(v), optionally in the presence of acatalyst, to form the corresponding polyurethane prepolymer.

[0055] The preparation of the polyurethane prepolymer in reaction stage(a₂) preferably takes place in such a way that the finely ground polyolcomponent (A) (iv) with an average particle size <150 μm and thepolymeric diol component (A)(v) are added or metered in to thepolyurethane preadduct from stage (a₁) within a period ranging fromseveral minutes to several hours. Given a corresponding process regimeand/or incomplete reaction, the polyurethane preadduct from stage (a₁)that is used in reaction stage (a₂) may possibly, alongside isocyanategroups and/or polyisocyanate monomers, contain hydroxyl groups which arestill free.

[0056] Component (A) (iv) is composed of at least one low molecularmass, anionically modifiable polyol or polyamine having one or morepolyisocyanate-reactive hydroxyl and/or amino groups and one or morepolyisocyanate-inert carboxylic and/or sulfonic acid groups, some or allof which can be converted in the presence of bases into carboxylateand/or sulfonate groups or are already in the form of carboxylate and/orsulfonate groups, and having an average molecular mass of from 100 to 1000 daltons (number average). As low molecular mass, anionicallymodifiable polyols it is possible to use, for example, hydroxypivalicacid (trade name HPA, Perstorp Specialty Chemicals AB),2-hydroxymethyl-3-hydroxypropanoic acid or dimethylolacetic acid,2-hydroxymethyl-2-methyl-3-hydroxypropanoic acid or dimethylolpropionicacid (trade name Bis-MPA, Perstorp Specialty Chemicals AB),2-hydroxymethyl-2-ethyl-3-hydroxypropanoic acid or dimethylolbutyricacid, 2-hydroxymethyl-2-propyl-3-hydroxypropanoic acid ordimethylolvaleric acid, citric acid, tartaric acid,[tris(hydroxymethyl)methyl]-3-aminopropanesulfonic acid (TAPS, RaschigGmbH), compounds based on 1,3-propane sulfone (Raschig GmbH) and/or3-mercaptopropanesulfonic acid, sodium salt (trade name MPS, RaschigGmbH) or mixtures thereof. These compounds may optionally also containamino groups in place of hydroxyl groups. Preference is given tobishydroxyalkanecarboxylic acids and/or bishydroxysulfonic acids and/ortheir alkali metal salts, having a molecular mass of from 100 to 499daltons, and especially 2-hydroxymethyl-2-methyl-3-hydroxypropanoic acidor dimethylolpropionic acid (trade name DMPA® from Trimet TechnicalProducts, Inc.).

[0057] Component (A) (v) is composed of from 0 to 20 parts by weight ofa polymeric polyol component having two or more polyisocyanate-reactivehydroxyl groups and further, polyisocyanate-inert hydrophilic groups,such as, for example, polyethylene oxide segments, having an averagemolecular mass of from 500 to 5 000 daltons (number average). It ispreferred to use reaction products of poly(ethyleneoxide[co/block/ran-propylene oxide]) monoalkyl ethers, a diisocyanate,and diethanolamine.

[0058] The reaction conditions for carrying out reaction stages (a₁) and(a₂) are not particularly critical. In reaction stages (a₁) and (a₂) thereaction mixture is stirred under inert gas atmosphere at preferablyfrom 60 to 120° C., in particular from 80 to 120° C., utilizing theexothermic heat of the polyaddition reaction, until the calculated ortheoretical NCO content is reached. The reaction times required aresituated in the region of several hours and are decisively influenced byreaction parameters, such as the reactivity of the components, thestoichiometry of the components, and the temperature.

[0059] Components (A) and (B) in reaction stages (a₁) and/or (a₂) can bereacted in the presence of a catalyst customary for polyadditionreactions with polyisocyanates. Where needed, these catalysts are addedin amounts of from 0.01 to 1% by weight, based on components (A) and(B). Customary catalysts for polyaddition reactions with polyisocyanatesare, for example, dibutyltin oxide, dibutyltin dilaurate (DBTL),triethylamine, tin(II) octoate, 1,4-diazabicyclo[2.2.2]octane (DABCO),1,4-diazabicyclo[3.2.0]-5-nonene (DBN), and1,5-diazabicyclo[5.4.0]-7-undecene (DBU).

[0060] The anionically modifiable polyurethane prepolymer from reactionstage (a₂) is reacted in the subsequent reaction stage (a₃) fully orpartly with 0 to 15 parts by weight of a polyfunctional chain terminatorcomponent (D) under conditions in which in each case only one reactivegroup or component (D) reacts with an isocyanate group of thepolyurethane preadduct. Reaction stage (a₃) is preferably conducted at atemperature of from 60 to 120° C., in particular at from 80 to 100° C.

[0061] The chain terminator component (D) is composed preferably of oneor more polyols, polyamines and/or polyamino alcohols having three ormore isocyanato-reactive hydroxyl and/or primary and/or secondary aminogroups and an average molecular mass of from 50 to 500 daltons (numberaverage), of which one reacts with the polyurethane preadduct. As asuitable chain terminator component (D) it is possible to use, forexample, diethanolamine, trimethylolpropane, ditrimethylolpropane,pentaerythritol, dipentaerythritol, carbohydrates and/or derivativesthereof. It is preferred to use aliphatic or cycloaliphatic polyolsand/or polyamines and/or amino alcohols, and especially diethanolamineand/or trimethylolpropane.

[0062] The chain terminator component (D) is added in an amount suchthat the degree of chain termination, based on the free isocyanategroups of the polyurethane prepolymer, formed from components (A) and(B), is from 0 to 100 equivalent%.

[0063] The functionalized and anionically modifiable polyurethaneoligomer or polymer from reaction stage (a₃), which has two or morereactive groups per chain end and a total functionality of ≧4, isreacted in the subsequent reaction stage (a₄) with from 0.1 to 10 partsby weight of a neutralizing component (E) for partial or completeneutralization of the carboxylic and/or sulfonic acid groups (directneutralization). Reaction stage (a₄) is conducted preferably at atemperature of from 40 to 65° C., in particular at around 50° C.

[0064] The neutralizing component (E) is composed of one or more bases,which serve to neutralize some or all of the carboxylic and/or sulfonicacid groups. Where component (A) (iv) is already in the form of itssalts, there is no need for neutralizing component (E). As suitablebases it is possible to use, for example, tertiary amines such asN,N-dimethylethanolamine, N-methyldiethanolamine, triethanolamine,N,N-dimethyl-isopropanolamine, N-methyldiisopropanolamine,triiso-propylamine, N-methylmorpholine, N-ethylmorpholine,triethylamine, ammonia or alkali metal hydroxides such as lithiumhydroxide, sodium hydroxide, and potassium hydroxide. It is preferred touse tertiary amines and especially triethylamine.

[0065] The neutralizing component (E) is added in an amount such thatthe degree of neutralization, based on the free carboxylic and/orsulfonic acid groups of the polyurethane oligomer or polymer formed fromcomponents (A), (B), and (D) is from 60 to 100 equivalent %, preferablyfrom 80 to 95 equivalent %. With neutralization, carboxylate and/orsulfonate groups are formed from the carboxylic and/or sulfonic acidgroups, and serve for the anionic modification or stabilization of thepolyurethane dispersion.

[0066] The functionalized and anionically modified polyurethane oligomeror polymer from reaction stage (a₄) is dispersed in the subsequentreaction stage (a₅) in from 40 to 120 parts by weight of water, whichcan additionally contain from 0 to 50 parts by weight of a formulatingcomponent (F) (in situ formulation). Reaction stage (a₅) is preferablyconducted at a temperature of from 30 to 50° C., in particular at around40° C. Where needed, the water, which can additionally contain theformulating component (F), can also be dispersed into thepolyfunctional, anionically modified polyurethane oligomer or polymer.

[0067] Reaction stages (a₄) and (a₅) can also be integrated with oneanother such that component (E) is added to the water prior todispersing (indirect neutralization). If required it is also possible toemploy a combination of direct and indirect neutralization.

[0068] On dispersing, the polyurethane prepolymer is transferred to thedispersing medium and forms an aqueous solution or dispersion ofoptionally hydroxy- and/or amino-functional oligo- or polyurethanes. Theanionically modified polyurethane oligomer or polymer either formsmicelles, which have stabilizing carboxylate and/or sulfonate groups onthe surface and reactive isocyanate groups inside, or is in solution inthe aqueous phase. All cationic counterions to the anionic carboxylateand/or sulfonate groups are in solution in the dispersing medium. Theterms “dispersing” and “dispersion” comprehend the possibility ofsolvated and/or suspended components being present as well as dispersedcomponents with a micellar structure.

[0069] The hardness of the water used is immaterial to the process, and,consequently, the use of distilled or demineralized water isunnecessary. Higher levels of hardness result in a further reduction inthe water absorption of the aqueous, highly crosslinked two-componentpolyurethane coating systems, without adversely affecting their materialproperties.

[0070] The formulating component (F) comprises defoamers,devolatilizers, lubricant and leveling additives, radiation curingadditives, dispersing additives, substrate wetting additives,hydrophobicizers, Theological additives, such as polyurethanethickeners, coalescence aids, flatting agents, adhesion promoters,antifreeze agents, antioxidants, UV stabilizers, bactericides,fungicides, further polymers and/or polymer dispersions, and fillers,pigments, flatting agents or a suitable combination thereof. Theindividual formulating ingredients are to be regarded as inert.

[0071] In the subsequent reaction stage (a₆), the functionalized andanionically modified polyurethane oligomer or polymer from reactionstage (a₅), which may be only partly chain-terminated, is reacted withfrom 0 to 10 parts by weight of a chain extender component (G). Reactionstage (a₆) is preferably conducted at a temperature of from 30 to 50°C., in particular at around 40° C.

[0072] Reaction stages (a₅) and (a₆) may also be integrated with oneanother such that component (G) is added to the water prior todispersing.

[0073] The chain extender component (G) is composed of a polyaminehaving two or more polyisocyanate-reactive amino groups and an averagemolecular mass of from 50 to 500 daltons (number average). As suitablepolyamines it is possible to use, for example, adipic dihydrazide,ethylenediamine, diethylenetriamine, triethylenetetr-amine,tetraethylenepentamine, pentaethylenehexamine, dipropylenetriamine,hexamethylenediamine, hydrazine, isophoronediamine,N-(2-aminoethyl)-2-aminoethanol, adducts of salts of2-acrylamido-2-methylpropane-1-sulfonic acid (AMPS®) andethylenediamine, adducts of salts of (meth)acrylic acid withethylenediamine, adducts of 1,3-propane sulfone and ethylenediamine, orany desired combinations of these polyamines. It is preferred to usedifunctional primary amines, and especially ethylenediamine.

[0074] The chain extender component (G) is added in an amount such thatthe degree of chain extension, based on the free isocyanate groups ofthe polyurethane oligomer or polymer formed from components (A), (B),(D), and (E), is from 0 to 95 equivalent %. The chain extender component(G) can be diluted in pre-withdrawn fractions of the water, in a weightratio from 1:1 to 1:10, in order to suppress the additional exothermicheat by the hydration of the amines.

[0075] The (partial) chain extension leads to an increase in themolecular mass of the polyurethane oligomer or polymer. The chainextender component (G) reacts with reactive isocyanate groupssubstantially more rapidly than water. In the following reaction stage(a6) any remaining free isocyanate groups are fully chain-extended withwater.

[0076] The solids content in terms of polyurethane oligomer or polymercomposed of components (A), (B), (D), (E) and (G) is adjusted to from 35to 60% by weight, preferably from 40 to 50% by weight, based on thetotal amount of the aqueous binder component composed of components (A)to (E) and (G).

[0077] The average particle size of the micelles of the aqueous bindercomponent composed of components (A) to (E) and (G) is preferably from10 to 300 nm.

[0078] The average molecular mass of the polyurethane oligmer or polymercomposed of components (A), (B), (D), (E) and (G) is preferably from 2000 to 20 000 daltons (number average).

[0079] The carboxylate and/or sulfonate group content of thepolyurethane oligomer or polymer composed of components (A), (B), (D),(E) and (G) is adjusted preferably to from 10 to 45 meq·(100 g)⁻¹,especially preferably to from 15 to 30 meq·(100 g)⁻¹.

[0080] The binder component is in the form of a dispersion ormolecularly disperse solution of optionally hydroxy- and/oramino-functional oligourethanes and/or polyurethanes which are dilutablewith water and are situated within a pH range from 6 to 9. They mayoptionally additionally contain further water-dilutable organicpolyhydroxy compounds, such as water-soluble alcohols having more thantwo hydroxyl groups, e.g., glycerol, trimethylolpropane,1,2,3-butanetriol, 1,2,6-hexanetriol, pentaerythritol or sugars, as aresult of which it is possible to carry out corresponding modificationof the technical coatings properties of the cured coating.

[0081] These dispersions of solutions are stabilized by the presence ofionically hydrophilic groups, such as carboxylate, sulfonate or otherhydrophilic groups, for example, which are obtained by neutralizing someor all of the corresponding acid groups.

[0082] Optionally, finally, in reaction stage (b), the binder componentfrom reaction stage (a₅) or (a₆) is reacted with the optionallyhydrophilically modified crosslinker component (H), preferably in aratio of from 3:1 to 5:1 (based on the respective weight), thecrosslinker component (H) being added to the binder component to give,following application, a highly crosslinked anti-graffiti andanti-soiling polyurethane coating system. Reaction stage (b) ispreferably conducted at a temperature of from 20 to 40° C., inparticular at around 20° C.

[0083] The crosslinker component (H) is composed of water-dispersiblepolyisocyanates having aliphatically and cycloaliphatically and/oraromatically attached isocyanate groups and containing from 0 to 20parts by weight of an organic solvent. The aliphatic polyisocyanates arepreferred to the aromatic polyisocyanates. Particularly suitable are the“paint polyisocyanates” well known in polyurethane chemistry, based onbis(4-isocyanatocyclohexyl)methane (H₁₂MDI), 1,6-diisocyanatohexane(HDI), 1-isocyanato-5-isocyanatomethyl-3,3,5-trimethylcyclohexane (IPDI)or combinations thereof. The term “paint polyisocyanates” characterizesderivatives of these diisocyanates which contain allophanate, biuret,carbodiimide, isocyanurate, uretdione and/or urethane groups and inwhich the residual monomeric diisocyanate content has been reduced to aminimum in accordance with the state of the art. Besides these it isalso possible to use hydrophilically modified polyisocyanatesobtainable, for example, by reacting “paint polyisocyanates” withpolyethylene glycol. As suitable polyisocyanates it is possible to use,for example, commercial HDI isocyanurates without (trade name RhodocoatWT 2102, Rhodia AG) or with hydrophilic modification (trade name BasonatP LR 8878, BASF AG, trade name Desmodur DA or Bayhydur 3100 from BayerAG.

[0084] To prepare the ready-to-use aqueous fluoromodified two-componentpolyurethane coating composition the crosslinker components (H) (“curingagent”, part B) is mixed shortly before application into the bindercomponent comprising components (A) to (G) (“stock varnish”, part A). Inorder to obtain trouble-free emulsification it is advisable to dilutethe polyisocyanates with small amounts of organic solvents, such asdipropylene glycol dimethyl ether (Proglyde DMM®), butyl (di)glycolacetate or butyl acetate, for example. Simple emulsifying techniques,operating for example with a mechanical stirring mechanism (drill withstirrer), are generally sufficient to bring about homogeneousdistribution of the components. The amounts of binder component and ofthe crosslinker component are such that the NCO/(OH+NH₍₂₎) equivalentratio of the isocyanate groups of the crosslinker component and of thehydroxyl and/or amino groups of the binder component is adjusted to from1.1 to 1.6, preferably from 1.2 to 1.4.

[0085] In this way it is possible to obtain transparent scratchproofcoatings having very low surface energies and, owing to a highcrosslinking density, having outstanding properties. This applies bothto the processing properties and to the surface properties andmechanical properties, in conjunction with very good solvent resistanceand chemical resistance. Because of the fluorinated side chains and thecomparatively low hydrophilic group content of the binder component, thecoatings additionally feature excellent water resistance.

[0086] The aqueous, highly crosslinked anti-graffiti and anti-soilingpolyurethane coating system of the invention is applied by the methodsknown from coating technology, such as flow coating, pouring, knifecoating, rolling, spraying, brushing, dipping, and roller coating, forexample.

[0087] The drying and curing of the coatings take place generally atstandard (exterior and interior) temperatures in the range from 5 to 40°C., i.e., without special heating of the coating, though depending onthe particular utility may also take place at higher temperatures in therange from 40 to 100° C.

[0088] The present invention further provides for the use of theaqueous, highly crosslinked and anti-graffiti and anti-soilingpolyurethane coating of the invention in the construction sector or inthe industrial sector in the form of formulated or unformulated,chemically stable and lightfast paint and/or coating systems for thesurfaces of mineral building materials, such as concrete, plaster,ceramic, clay, and cement, for example, and also for the surfaces ofglass, rubber, wood and wood-based materials, plastic, metal, paper,composites or leather.

[0089] The aqueous, highly crosslinked anti-graffiti and anti-soilingpolyurethane coating systems proposed in accordance with the inventionare also suitable, individually or in combination, for the constructionof systems for

[0090] (α) dirt-repellent anti-graffiti coatings on plastic, wood ormetal for traffic signs or rail wagons, for example,

[0091] (β) dirt-repellent coatings of rotors for wind power plants,

[0092] (γ) dirt-repellent interior floor coverings and exterior groundcoverings.

[0093] The surface energy of a dried film produced on the basis of acoating system according to the invention is preferably less than 18.6mN/m, the literature value for Teflon®.

[0094] The examples which follow are intended to illustrate theinvention in more detail.

EXAMPLES Example 1 Fluoromodified Diol Component (T-Bone)

[0095] A four-necked flask equipped with KPG stirrer, reflux condenser,internal thermometer and nitrogen blanketing was charged with 0.1 mol of2,4-tolylene diisocyanate (TDI) (Desmodur T 80, Bayer AG) in solution in28.8 g of N-methylpyrrolidone (NMP) under nitrogen blanketing and thisinitial charge was cooled to about 15-20° C. Crystallization of2,4-tolylene diisocyanate (TDI) ought to be avoided without fail.Following the addition of 2 drops of dibutyltin dilaurate (DBTL)catalyst, an equimolar amount of fluoroalcohol (e.g., Zonyl® BA, Du Pontde Nemours) was added slowly dropwise over the course of about 1 h, withcooling. After the end of the dropwise addition the mixture was stirredat the same temperature for 1 h until the desired NCO value was reached.The preadduct was subsequently added slowly dropwise with cooling to anequimolar amount of diethanolamine (DEA) in the form of a mixture with3.0 g of N-methylpyrrolidone (NMP).

[0096] The reaction is at an end when the NCO value has dropped to zero.

Example 2 Hydroxy-Functional Fluoromodified Polyurethane DispersionBased on Polycarbonate

[0097] In a four-necked flask equipped with KPG stirrer, refluxcondenser, thermometer and nitrogen blanketing a mixture of 12.36 g offluoromodified diol component (see example 1; contains 3.71 g ofN-methylpyrrolidone (NMP)) and 49.72 g of isophorone diisocyanate(Vestanat® IPDI, Degussa AG) was stirred in the presence of 0.1 g ofdibutyltin dilaurate (DBTL) catalyst at 80-90° C. under nitrogenblanketing for 1.5 h. Following the addition of 8.40 g ofdimethylol-propionic acid (DMPA®), 100.00 g of a polycarbonatediolhaving a hydroxyl number of 56 mg KOH·g⁻¹ (Desmophen® C 200, Bayer AG)and 26.29 g of N-methylpyrrolidone (NMP) to the preadduct the mixturewas stirred further at 80-90° C. under nitrogen blanketing for about 50min until the calculated NCO content was reached (theoretical: 4.24% byweight). The course of the reaction was monitored by acidimetry.

[0098] The prepolymer was then dispersed with intensive stirring in233.48 g of water, to which 6.02 g of triethylamine (TEA) had been added(indirect neutralization), and was subsequently chain-extended with16.57 g of N-(2-aminoethyl)-2-aminoethanol (50% strength aqueoussolution).

[0099] This gave a stable polyurethane dispersion having the followingcharacteristics: Characteristics Milky-white liquid Solids content  40%by weight Charge density 34.57 meq · (100 g)⁻¹ Fluorine content 2.0% byweight

Example 3 Aqueous Fluoromodified Two-Component Polyurethane CoatingSystem Based on Example 2

[0100] Incorporation of Rhodocoat WT 2102, mixed (9:1) beforehand withdipropylene glycol dimethyl ether (Proglyde DMM®) using a mechanicalstirrer, gives a two-component polyurethane clearcoat material having anNCO/OH equivalent ratio of 1.3.

[0101] Component Parts by weight Description Component Parts by weightDescription PART A Example 2   991.00 polyurethane dispersion Byk 024   3.00 defoamer Tego Wet 500    3.00 wetting agent Edaplan LA 413    3.00leveling additive Total: 1 000.00 stock varnish PART B Rhodocoat WT 2102  50.00 water-dispersible polyisocyanate Proglyde ® DMM    5.56 solventTotal:   55.56 curing agent

Example 4 Hydroxy-Functional Fluoromodified Oligourethane Dispersion,Chain-Terminated with Trimethylolpropane (TMP)

[0102] In a four-necked flask equipped with KPG stirrer, refluxcondenser, thermometer and nitrogen blanketing a mixture of 12.15 g offluoromodified diol component (see example 1; contains 3.65 g ofN-methylpyrrolidone (NMP)), 100.00 g of a polycarbonatediol having ahydroxyl number of 56 mg KOH·g⁻¹ (Desmophen® C 200, Bayer AG) and 43.55g of isophorone diisocyanate (Vestanat® IPDI, Degussa AG) was stirred inthe presence of 0.1 g of dibutyltin dilaurate (DBTL) catalyst at 80-90°C. under nitrogen blanketing for 2.0 h. Following the addition of 4.90 gof dimethylol-propionic acid (DMPA®) in solution in 11.35 g ofN-methylpyrrolidone (NMP) to the preadduct, the mixture was stirredfurther at 80-90° C. under nitrogen blanketing until the calculated NCOcontent was reached (theoretical: 4.18% by weight). The course of thereaction was monitored by acidimetry. Subsequently, 26.30 g oftrimethylolpropane in solution in 25.00 g of N-methylpyrrolidone (NMP)were added and the mixture was stirred at 80-90° C. for 4 h more untilthe NCO value had dropped to zero. After cooling to 60° C., theprepolymer was neutralized directly with 3.33 g of triethylamine (TEA).The prepolymer was then dispersed in 240.00 g of water with intensivestirring.

[0103] This gave a stable oligourethane dispersion having the followingcharacteristics: Characteristics Semitranslucent liquid Solids content 40% by weight Charge density 19.57 meq · (100 g)⁻¹ Fluorine content2.0% by weight

Example 5 Aqueous Fluoromodified Two-Component Polyurethane CoatingSystem (Highly Crosslinked) Based on Example 4

[0104] Incorporation of Rhodocoat WT 2102, mixed (9:1) beforehand withdipropylene glycol dimethyl ether (Proglyde DMM®) using a mechanicalstirrer, gives a two-component polyurethane clearcoat material having anNCO/OH equivalent ratio of 1.1. Component Parts by weight DescriptionPART A Example 4   991.00 oligourethane dispersion Byk 024    3.00defoamer Tego Wet 500    3.00 wetting agent Edaplan LA 413    3.00leveling additive Total: 1 000.00 stock varnish PART B Rhodocoat WT 2102  202.40 water-dispersible polyisocyanate Proglyde ® DMM   22.49 solventTotal:   224.89 curing agent

Example 6 Fluoromodified Polyurethane Dispersion Based on Polyester

[0105] In a four-necked flask equipped with KPG stirrer, refluxcondenser, thermometer and nitrogen blanketing a mixture of 12.43 g offluoromodified diol component (see example 1; contains 3.73 g ofN-methylpyrrolidone (NMP)) and 102.16 g of isophorone diisocyanate(Vestanat® IPDI, Degussa AG) was stirred in the presence of 0.1 g ofdibutyltin dilaurate (DBTL) catalyst at 80-90° C. under nitrogenblanketing for 1.5 h. Following the addition of 14.00 g of1,4-butanediol, 15.00 g of dimethylolpropionic acid (DMPA®), 100.00 g ofa polyester diol having a hydroxyl number of about 56.1 mg KOH·g⁻¹(Bester® 42 H, Poliolchimica S.p.A.), all in solution in 46.27 g ofN-methylpyrrolidone (NMP), the mixture was stirred further at 80-90° C.under nitrogen blanketing for one hour more until the calculated NCOcontent was reached (theoretical: 3.81% by weight). The course of thereaction was monitored by acidimetry.

[0106] The prepolymer was then dispersed with intensive stirring in341.41 g of water, to which 11.32 g of triethylamine (TEA) had beenadded (indirect neutralization), and was subsequently chain-extendedwith 33.12 g of ethylenediamine (16.7% strength aqueous solution).

[0107] This gave a stable polyurethane dispersion having the followingcharacteristics: Characteristics Semitranslucent liquid Solids content 38% by weight Charge density 43.55 meq · (100 g)⁻¹ Fluorine content1.5% by weight

[0108] Surface Energies of Cured Films of the Aqueous Fluoro-ModifiedPolyurethane Coating Systems of the Invention

[0109] The aqueous fluoromodified two-component polyurethane coatings,in accordance with examples 3, 5, and 6, were drawn down using doctorblade applicators onto glass plates (wet film thickness 150 μm) and thefilms were subsequently dried at room temperature. After 7 days theywere determined by means of the sessile drop method, with the contactangles of a series of apolar liquids (hexadecane, dodecane, decane andoctane) on the film surfaces being measured.

[0110] The test results are set out in the following table. Comparativedispersion Ex. 3 Ex. 5 Ex. 6 (not modified) Film clear clear clear cleartransparency Surface energy 15.8 19.6 21.7 44.3 of a dried film [mN/m]

1. An aqueous fluoromodified polyurethane system for one- ortwo-component anti-graffiti and anti-soiling coatings, obtainable by (a)preparing a binder component based on an aqueous solution or dispersionof optionally hydroxyl- and/or amino-functional obligo- and/orpolyurethanes having fluorinated side chains, for which (a₁) from 2.5 to12 parts by weight of a fluoromodified polyol component (A)(i) havingtwo or more isocyanate-reactive hydroxyl groups and a molecular mass offrom 500 to 2,000 daltons, where as component (A)(i) reaction productsand/or macromonomers of monofunctional fluoroalcohols, aliphatic and/oraromatic diisocyanates, and diethanolamine are used, the fluoroalcoholsbeing perfluoroalkyl alcohols having terminal methylene groups(hydrocarbon spacers) of the general formula F(CF₂)_(x)—(CH₂)_(y)—OHwithx=4-20 and y=1-6  or hexafluoropropene oxide (HFPO) oligomer alcohols ofthe general formula CF₃CF₂CF₂O—(CF(CF₃)(CF₂O)_(z)—CF(CF₃)CH₂—OH, withz=1-10  or mixtures of these, from 10 to 50 parts by weight of a highmolecular mass polyol component (A)(ii) having two or morepolyisocyanate-reactive hydroxyl groups and a molecular mass of from 500to 6,000 daltons, and from 0 to 10 parts by weight of a low molecularmass polyol component (A)(iii) having two or morepolyisocyanate-reactive hydroxyl groups and a molecular mass of from 50to 499 daltons are reacted with from 2 to 30 parts by weight of apolyisocyanate component (B), composed of at least one polyisocyanate,polyisocyanate derivative or polyisocyanate homolog having two or morealiphatic or aromatic isocyanate groups, with the addition of from 0 to25 parts by weight of a solvent component (C) composed of an inertorganic solvent, optionally in the presence of a catalyst, (a₂) thepolyurethane preadduct from stage (a₁) is reacted, optionally in thepresence of a catalyst, with from 0.1 to 10 parts by weight of a lowmolecular mass, anionically modifiable polyol component or polyaminecomponent (A) (iv) having two or more polyisocyanate-reactive hydroxyland/or amino groups and one or more inert carboxylic and/or sulfonicacid groups, some or all of which can be converted by means of basesinto carboxylate and/or sulfonate groups, respectively, or are alreadyin the form of carboxylate and/or sulfonate groups, having a molecularmass of from 100 to 1,000 daltons and/or with from 0 to 20 parts byweight of a polymeric polyol component (A)(v) having two or morepolyisocyanate-reactive hydroxyl groups and further,polyisocyanate-inert, hydrophilic groups, having a molecular mass offrom 500 to 5,000 daltons, (a₃) some or all of the free isocyanategroups of the polyurethane prepolymer from stage (a₂) are reacted withfrom 0 to 15 parts by weight of a polyfunctional chain terminatorcomponent (D) having three or more isocyanato-reactive hydroxyl and/orprimary and/or secondary amino groups and a molecular mass of from 50 to500 daltons, of which one reacts with the polyurethane prepolymer, (a₄)the polyfunctional polyurethane oligomer or polymer from stage (a₃) isadmixed, for neutralization of some or all of the acid groups, with from0.1 to 10 parts by weight of a neutralizing component (E), and then (a₅)the neutralized polyurethane oligomer or polymer from stage (a₄) isdispersed in from 40 to 120 parts by weight of water, which may alsocontain from 0 to 50 parts by weight of a formulating component (F), and(a₆) the only partly chain-terminated polyurethane oligomer or polymerfrom stage (a₅) is further reacted with from 0 to 10 parts by weight ofa chain extender component (G) having two or more isocyanato-reactiveprimary and/or secondary amino groups and a molecular mass of from 50 to500 daltons, and, optionally, (b) subsequently reacting the bindercomponent from stages (a₄), (a₅) or (a₆) with from 20 to 100 parts byweight of a crosslinker component (H), said crosslinker component (H)comprising water-dispersible polyisocyanates having aliphatically and/orcycloaliphatically and/or aromatically attached isocyanate groups andpossibly containing from 0 to 20 parts by weight of an organic solvent.2. The polyurethane system of claim 1, wherein the high molecular masspolyol component (A) (ii) is composed of a hydrophobically modifiedpolyether- and/or polyester- and/or polycaprolactone- and/orpolycarbonate-polyol and/or α,ω-polymethacrylatediol or of suitablecombinations thereof.
 3. The polyurethane system of claim 2, wherein ascomponent A(ii) linear and/or difunctional polyester- and/orpolycaprolactone- and/or polycarbonate-polyols having a molecular massof from 1,000 to 3,000 daltons are used.
 4. The polyurethane system ofclaim 1, wherein as component (A)(iii) 1,4-butanediol and/or2-methyl-1,3-propanediol and/or neopentyl glycol is used.
 5. Thepolyurethane system of claim 1, wherein component (A)(iv) is abishydroxyalkanecarboxylic acid or bishydroxy-sulfonic acid and/oralkali metal salts thereof having a molecular mass of from 100 to 1,000daltons.
 6. The polyurethane system of claim 5, wherein thebishydroxyalkanecarboxylic acid2-hydroxymethyl-2-methyl-3-hydroxypropionic is acid ordimethylolpropionic acid.
 7. The polyurethane system of claim 1, whereinas component (A)(v) reaction products of poly(ethylene oxide[co/block/ran-propylene oxide]) monoalkyl ethers, a diisocyanate, anddiethanolamine are used.
 8. The polyurethane system of claim 1, whereinas polyfunctional chain terminator component (D) aliphatic orcycloaliphatic polyols and/or polyamines and/or amino alcohols are used.9. The polyurethane system of claim 8, wherein as polyfunctional chainterminator component (D) diethanolamine, trimethylolpropane,pentaerythritol, carbohydrates and/or derivatives thereof are used. 10.The polyurethane system of claim 1, wherein as formulating component (F)defoamers, devolatilizers, lubricant and leveling additives, radiationcuring additives, dispersing additives, substrate wetting additives,hydrophobicizing agents, rheological additives, such as polyurethanethickeners, coalescence aids, flatting agents, adhesion promoters,antifreeze agents, antioxidants, UV stabilizers, bactericides,fungicides, further polymers and/or polymer dispersions, and alsofillers, pigments, flatting agents, or suitable combinations thereof areused.
 11. The polyurethane system of claim 1, wherein the NCO/OHequivalent ratio of components (A) and (B) has a value of from 1.2 to2.5, preferably from 1.5 to 2.25.
 12. The polyurethane system of claim1, wherein as crosslinker component (H) water-dispersiblepolyisocyanates having aliphatically and/or cycloaliphatically and/oraromatically attached isocyanate groups are used which contain from 0 to20 parts by weight of an organic solvent.
 13. The polyurethane system ofclaim 1, wherein reaction stages (a₁) and (a₂) are conducted in thepresence of from 0.01 to 1% by weight, based on components (A) and (B),of a catalyst customary for polyaddition reactions with polyisocyanates.14. The polyurethane system of claim 1, wherein the neutralizingcomponent (E) is added in an amount such that the degree ofneutralization, based on the free carboxylic and/or sulfonic acid groupsof the polyurethane oligomer or polymer formed from components (A), (B),(D), (E), and (G), is from 60 to 100 equivalent %, preferably from 80 to95 equivalent %.
 15. The polyurethane system of claim 1, wherein thechain terminator component (D) is added in an amount such that the levelof chain termination, based on the free isocyanate groups of thepolyurethane prepolymer formed from components (A) and (B), is from 0 to100 equivalent %.
 16. The polyurethane system of claim 1, wherein thechain extender component (G) is added in an amount such that the degreeof chain extension, based on the free isocyanate groups of thepolyurethane oligomer or polymer formed from components (A), (B), (D),and (E), is from 0 to 95 equivalent %.
 17. The polyurethane system ofclaim 1, wherein the solids content in terms of polyurethane oligomer orpolymer composed of components (A), (B), (D), (E), and (G) is adjustedto from 35 to 60% by weight, preferably from 40 to 50% by weight, basedon the total amount of the aqueous binder component composed ofcomponents (A) to (E) and (G).
 18. The polyurethane system of claim 1,wherein the average particle size of the micelles of the aqueous bindercomponent composed of components (A) to (E) and (G) is from 10 to 300nm.
 19. The polyurethane system of claim 1, wherein the polyurethaneoligomer or polymer composed of components (A), (B), (D), (E), and (G)has an average molecular mass of from 2,000 to 100,000 daltons.
 20. Thepolyurethane system of claim 1, wherein the ratio of crosslinkercomponent (H) to the binder component formed from components (A) to (E)or (A) to (F) is from 1:3 to 1:5.
 21. A process for preparing theaqueous polyurethane system of claim 1 (a₁) reacting components (A) (i),(A) (ii), (A) (iii), (B) and (C) optionally in the presence of acatalyst, to form a polyurethane preadduct, some or all of the hydroxylgroups of components (A) (i), (A) (ii) and (A) (iii) being reacted withthe isocyanate groups of component (B), (a₂) reacting the polyurethanepreadduct from reaction stage (a₁) with components (A) (iv) and (A) (v),(a₃) optionally reacting the anionically modifiable polyurethaneprepolymer from reaction stage (a₂) with component (D), in each caseonly one reactive group of component (D) reacting with an isocyanategroup of the polyurethane preadduct, (a₄) reacting the functionalizedand anionically modifiable polyurethane oligomer or polymer fromreaction stage (a₃), which optionally has two or more reactive groupsper chain end and a total functionality of ≧4, with component (E) forcomplete or partial neutralization, and subsequently (a₅) dispersing thefunctionalized and anionically modified polyurethane oligomer or polymerfrom reaction stage (a₄) in water, which optionally additionallycomprises component (F), (a₆) optionally reacting the only partlychain-terminated, functionalized, and anionically modified polyurethaneoligomer or polymer from stage (a₅) with component (G), and optionally(b) reacting the binder component from reaction stage (a₅) or reactionstage (a₆) with the optionally hydrophilically modified crosslinkercomponent (H), the crosslinker component (H) being added to the bindercomponent and, following application, a highly crosslinked anti-graffitiand anti-soiling coating system being obtained.
 22. The process of claim21, wherein stages (a₄) and (a₅) are integrated with one another suchthat component (E) is added to the water prior to dispersing.
 23. Theprocess of claim 21, wherein stages (a₅) and (a₆) are integrated withone another such that component (G) is added to the water prior todispersing.
 24. The process of claim 21, wherein reaction stages (a₁) to(a₃) are conducted at a temperature of from 60 to 120° C., preferablyfrom 80 to 100° C.
 25. The process of claim 21, wherein reaction stage(a₄) is conducted at a temperature of from 40 to 65° C., preferably ataround 50° C.
 26. The process of claim 21, wherein reaction stages (a₅)and (a₆) are conducted at from 30 to 50° C., preferably at around 40° C.27. The process of claim 21, wherein reaction stage (b) is conducted ata temperature of from 20 to 40° C., preferably at around 20° C.
 28. Amineral building material comprising the unformulated aqueousfluoromodified one- or two-component polyurethane system of claim
 1. 29.The mineral building material of claim 28, wherein the polyurethanesystem is used, individually or in combination, for a system for (1)dirt-repellent anti-graffiti coatings on plastic, wood or metal fortraffic signs or rail wagons, for example, (2) dirt-repellent coatingsof rotors for wind power plants, (3) dirt-repellent interior floorcoverings and exterior ground coverings.